added return to previous directory before cleanup call

[AlReka]

#310 (comment)

[realtime-neil]

That's not the "previous" directory. That's the parent directory.

You can change to the previous directory by

cd -

-

When a <hyphen-minus> is used as the operand, this shall be equivalent to the command:

    cd "$OLDPWD" && pwd

which changes to the previous working directory and then writes its name.

-- https://pubs.opengroup.org/onlinepubs/9699919799/utilities/cd.html

[megastep]

It might be a good idea to add a unit test for the cleanup script too.